Commercial refrigerated display cases are typically illuminated using lamps located inside the display case. When a consumer opens a door of the refrigerated display case, warmer more humid air located outside the display case flows into the display case, which contains cooler less humid air. Condensation and fog can accumulate on the lens or translucent cover of the lamp as the warmer more humid air cools inside the display case. Until the condensation evaporates from the lens, a reduction in the overall light output measured on the products displayed in the refrigerated display case results.
At present, most commercial refrigerated display cases are illuminated using fluorescent lamps. Fluorescent tubes radiate heat as power is delivered to the lamp to illuminate the lamp. Since the fluorescent tubes are cylindrical, the heat radiates in all directions around the tube. The heat that is radiated toward the lens of the fluorescent lamp warms the lens. The warm lens can prevent fog or condensation from forming on the lens because the moisture quickly dissipates into the air of the refrigerated display case.
More recently, light emitting diode (LED) lamps have been employed to illuminate the inside of refrigerated display cases. LED lamps are preferred because they consume less power (watts) than their fluorescent counterparts, which results in an energy savings. Since less power is being delivered to the LED lamp, as compared to a fluorescent lamp, there is less heat generated by the lamp to warm the lens (or translucent cover) that covers the LEDs. Moreover, as more efficient LEDs have been developed and the systems have been improved to direct the light toward more useful areas of the display case, the amount of power that is delivered to the LED lamp is further reduced.
In addition to consuming less power, lamps that employ LEDs do not dissipate very much heat via radiation. Instead, LED lamps found in refrigerated display cases conduct heat from the non-light emitting side of the LED into a heat sink, a large portion of which is spaced from the lens or translucent cover. Accordingly, it is difficult to use the heat generated by the LEDs to dissipate any fog or condensation that forms on the lens or translucent cover of the LED lamp.
Additionally, LED lamps that are used to illuminate refrigerated display cases are also only moderately sealed. In other words, the housing of the lamp assembly allows for the ingress of air and water into the housing, which can result in condensation forming on the inner (light entering) surface of the lens or translucent cover for the LED lamp.